More than any other single group, health-care workers bore the brunt of the covid-19 pandemic. In the early days and weeks of the crisis, doctors, nurses and emergency medical technicians were hailed as superheroes — immortalized in graffiti and balcony ovations from New York City to Paris and Madrid. But as the months and years passed, the astonishing casualties from covid-19 — more than 1 million lives lost in the United States and nearly 7 million globally — led to exhaustion, burnout and trauma, as well as infection and deaths among front-line workers. Workforce shortages and unrelenting stress added to their hardships, even as the public applause for their contributions…